This invention relates in general to a universal joint including a cross having a plurality of bearing cups supported on respective trunnions. In particular, this invention relates to an improved structure positively retaining the bearing cups on the trunnions prior to assembly in a drive train system.
Drive train systems are widely used for generating power from a source and for transferring such power from the source to a driven mechanism. Frequently, the source generates rotational power, and such rotational power is transferred from the source to a rotatably driven mechanism. For example, in most land vehicles in use today, an engine/transmission assembly generates rotational power, and such rotational power is transferred from an output shaft of the engine/transmission assembly through a driveshaft assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical driveshaft assembly includes a hollow cylindrical driveshaft tube having a pair of end fittings, such as a pair of tube yokes, secured to the front and rear ends thereof. The front end fitting forms a portion of a front universal joint that connects the output shaft of the engine/transmission assembly to the front end of the driveshaft tube. Similarly, the rear end fitting forms a portion of a rear universal joint that connects the rear end of the driveshaft tube to the input shaft of the axle assembly. The front and rear universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.
A typical universal joint includes a cross having a central body portion with four cylindrical trunnions extending outwardly therefrom. The trunnions are oriented in a single plane and extend at right angles relative to one another. A hollow cylindrical bearing cup is mounted on the end of each of the trunnions. Needle bearings or other friction-reducing structures are provided between the outer cylindrical surfaces of the trunnions and the inner cylindrical surfaces of the bearing cups to facilitate rotational movement of the bearing cups relative to the trunnions during operation of the universal joint. In the front universal joint of the above-described driveshaft assembly, the bearing cups supported on the first opposed pair of the trunnions on a front cross are connected to the front end fitting of the driveshaft assembly, while the bearing cups supported on the second opposed pair of the trunnions on the front cross are connected to an end fitting secured to the output shaft of the engine/transmission assembly. Similarly, in the rear universal joint of the above-described driveshaft assembly, the bearing cups supported on the first opposed pair of the trunnions on a rear cross are connected to the rear end fitting of the driveshaft assembly, while the bearing cups supported on the second opposed pair of the trunnions on the rear cross are connected to an end fitting secured to the input shaft of the axle assembly.
Frequently, the first and second universal joints are manufactured concurrently with the driveshaft tube at a first location, then shipped as a unit to a second location for assembly with the other components of the vehicle drive train system. In such a manufacturing process, the front and rear end fittings are initially secured to the ends of the driveshaft tube, then a universal joint is connected to each of the end fittings. Thus, for each of the universal joints, only one opposed pair of the bearing cups is connected to an end fitting and, therefore, positively retained on the respective trunnions. The other opposed pair of the bearing cups remains mounted on the respective trunnions, but is not positively retained thereon. Following installation on the end fittings, each of the universal joints is purged with lubricant. Such purging is well known in the art and involves the injection of lubricant within the cross at a relatively high pressure. The lubricant passes through bores formed through each of the trunnions so as to move into the regions of the bearings disposed between the bearing cups and the trunnions.
It is known to provide elastomeric seals about the open ends of the bearing cups to retain lubricant in the region between the outer surface of the trunnion and the inner surface of the bearing cup where the roller bearings are located. The elastomeric seals also function to prevent the entry of dirt and other contaminants into the regions where the roller bearings are located. Additionally, it is known to provide rigid dust guards about the open ends of the bearing cups to protectively cover the elastomeric seals, and further to prevent the entry of dirt and other contaminants into the regions where the roller bearings are located. In some instances, the elastomeric seal and rigid dust guard have been combined into a single seal and dust guard assembly.
In the past, the rigid dust guards have been utilized to retain the bearing cups on the trunnions during shipment from the manufacturing facility to the assembly facility, as described above. To accomplish this, it is known to form the dust guard having a first portion that frictionally engages the outer surface of the trunnion and a second portion that engages an annular groove formed in the outer surface of the bearing cup. Although this structure has been generally effective, it has been found that the bearing cups can still become dislodged during shipment if a large impact is applied thereto. Even if the bearing cups are not removed from the trunnions as a result of these impacts, they may become misaligned therewith. Such misalignment is undesirable. Thus, it would be desirable to provide an improved structure for positively retaining the bearing cups on the trunnions of a universal joint cross prior to assembly.